1. Field of the Invention
This invention relates to a latch device and more particularly to a relief type latch device in which, for example, a hingedly attached door can be locked in its closed position and the locked door can be opened by once slightly pushing it in the closing direction by the hand and then removing the hand therefrom.
2. Description of the Prior Art
Many latch devices for retaining the closed state of a door of an audio device, etc. have been proposed, in which there are provided a stationary cylinder and a sliding rod which are relatively movable with respect to each other, and a cam axially supported on the sliding rod is rotated during the reciprocal movement of the sliding rod to restrict the movement of the sliding rod in the vicinity of one end portion of the reciprocal movement (Japanese Utility Model Public Disclosures Nos. SHO 58-148160 and 60-11977, U.S. Pat. No. 4,616,861, British Pat. No. 2,060,761, U.S. patent application Ser. No. 877,710, etc.).
A latch device disclosed in the above-mentioned Japanese Utility Model Public Disclosures Nos. SHO 58-148160 and 60-11977 include a stationary cylinder having a hollow interior with one end open, a sliding rod having an inserting portion which is slidable within the stationary cylinder, and a spring means which is biased when the inserting portion is inserted into the stationary cylinder. The inserting portion is provided with a rotary cam formed with a V-shaped cut-out in each end and is rotatably mounted on one surface thereof. The stationary cylinder is provided at the inner wall surface thereof with a first projecting pawl for engaging in the cut-out at one end of the rotary cam so as to rotate the rotary cam by a small amount, and midway of the length thereof with a second projecting pawl for engaging in the cut-out at the other end of the rotary cam so as to further rotate the rotary cam by a small amount and fitting in the cut-out to retain the inserting portion in a state where the inserting portion is pushed in the hollow interior, and still further rotating the rotary cam to permit the inserting portion to pass when the inserting portion is pushed out of the hollow interior in the state where the rotary cam is perpendicular to the hollow interior.
However, the above-mentioned conventional latch device has such a shortcoming in that when the rotary cam rotates freely or reversely, poor engagement between both the cut-outs of the rotary cam and the first and second projections occurs, and the latch becomes unable to operate normally.
In order to prevent the free rotation and the reverse rotation of the rotary cam, it is possible to coat the rotary cam at the axially supporting portion thereof with a grease or the like so that the rotary cam will not rotate unexpectedly and/or to strictly maintain the size of the axially supporting portion so that rotation of the rotary cam will be restricted. However, these methods are causes for increasing the number of product inspection processes and the cost.